100% CPU on El Capitan with NS 6.4?

I have successfully installed and updated Norton Security (currently 6.4 build 36) on OS X El Capitan (10.11), but I am pretty steadily seeing very high CPU times, in the 98-100% range.  Mac is MacBook Pro Retina mid-2012.  This seems excessive, fan keeps ramping up.

Anyone else seeing it?

Any work-arounds or suggestions?